An Electronic Programme Guide (EPG) or Interactive Programme Guide (IPG) or Electronic Service Guide (ESG) is a digital guide to multicast and broadcast programs, typically displayed on-screen with functions allowing a viewer to navigate, select, and discover content (also called program, channel, service) by time, title, channel, genre, etc. by use of their remote control, a keyboard, or other input devices such as a phone keypad. The on-screen information may be delivered by a dedicated channel or assembled by the receiving equipment from information sent by each program channel.
By navigating through an ESG on a receiving device, users can see more information about the current program and about future programs. Typical elements of an ESG comprise a graphical user interface which enables the display of program titles, descriptive information such as a synopsis, actors, directors, year of production, and so on, the channel name and the programs on offer from subchannels such as pay-per-view and VOD (video-on-demand) services, program start times, genres and other descriptive metadata.
The ESG information is typically displayed on a grid with the option to select more information on each program. The ESG allows viewers to browse program summaries, to search by genre or channel, immediate access to the selected program, reminders, and parental control functions.
The ESG is typically sent within a broadcast transport stream, or in a special data channel alongside it. Of course, it can also be multicast to a selected groups of client devices. For example, The ATSC (American Television Standards Committee) standard for DTV (digital TV) uses tables sent in each station's PSIP (program and system information protocol). Herein, the PSIP is the protocol used for carrying metadata about each channel in the broadcast transport stream of a TV station and for publishing information about television programs so that viewers can select what to watch by title and description. Further, these tables are capable of containing the program start time and title, and additional program descriptive “metadata”.
In the broadcast network, all channels are always existent (or called available) on wire or wireless medium, thus the latency of channel changing is usually small. However, in a multicast network, upon a channel change request, the Internet Group Management Protocol (IGMP) is used to leave the current channel and join the selected channel. The IGMP is a communication protocol used to manage the membership of Internet Protocol multicast groups. The IGMP is used by a client device and its adjacent multicast routers to establish multicast group memberships when the client intends to join a multicast channel.
FIG. 1 is a message sequence chart illustrating a channel changing in an IP-based mobile TV network. A TV head end provides a plurality of channels, and a terminal is connected to the TV head end for receiving a channel. At the beginning the terminal views a channel A. Then the user browses the ESG and decides to change to the channel B. Corresponding instructions for changing channel are generated according to the selection of channel B in the ESG. Generally, the instructions for changing channel consist of instruction for leaving the current channel and instruction for joining the new channel by using the IGMP. The channel switching delay or channel changing delay is generally related to a time period starting at the time of terminal's sending an IGMP leave instruction and ending at the time of terminal's beginning to display the content of the new program.
Further, U.S. Pat. No. 6,563,830 discloses multicast registration of all multicast flows in an asynchronous transfer mode based emulated LAN, and in the application, it briefs the IGMP snooping.
WO2005045603 discloses a method for service selection and sorting. Specifically, service is attached with a type of a group comprising subscribed and unsubscribed. In order to facilitate a user to distinguish subscribed services from services of other types, the list of services is modified, e.g. highlighting subscription items, based on locally stored information concerning the accessibility of services (i.e. being stored in the user terminal) and user's service accessibility setting or input.
It is desirable to reduce the average time for tuning to a program.